The Stochastic Evolution of a Protocell: The Gillespie Algorithm in a Dynamically Varying Volume

We propose an improvement of the Gillespie algorithm allowing us to study the time evolution of an ensemble of chemical reactions occurring in a varying volume, whose growth is directly related to the amount of some specific molecules, belonging to the reactions set. This allows us to study the stochastic evolution of a protocell, whose volume increases because of the production of container molecules. Several protocell models are considered and compared with the deterministic models

Angiotensin type-2 (AT-2)-receptor activation reduces renal fibrosis in cyclosporine nephropathy: evidence for blood-pressure independent effect

Compound 21 (C21), selective agonist of AT2 receptors, shows antinflammatory effects in hypertension and nephroprotection in diabetes. The aim of this study was to evaluate the effects of C21 in cyclosporine nephropathy, which is characterized mainly by tubulo-interstitial fibrosis. Ten days before and during the experimental periods, low-salt diet was administered to Sprague Dawley rats. Cyclosporine-A (15mg/kg/day, i.p.) and cyclosporine-A plus C21 (0.3 mg/kg /day, i.p) were administered for 1 and 4 weeks. Control groups was left without any treatment. Blood pressure (plethysmographic method) and 24 hour albuminuria were measured once a week. At the end of the experiments, the kidneys were excised for histomorphometric analysis of renal fibrosis and for immunohistochemical evaluation of inflammatory infiltrates and type I and IV collagen expression.After 1 and 4 weeks, the rats treated with cyclosporine showed a significant increase (p <0.01) in blood pressure, no significant changes in albuminuria, a significant increase (p <0.01) in glomerular and tubulo-interstitial fibrosis and inflammatory infiltrates as compared to the control rats. Treatment with C21 did not modify the cyclosporine dependent increase of blood pressure, which was higher than in control rats, but after 4 weeks of treatment significantly reduced (p <0.01) glomerular and tubulo-interstitial fibrosis, type 1 collagen expression and macrophage infiltration, as compared to rats treated with cyclosporine.The administration of C21 showed a protective effect on cyclosporine nephropathy, decreasing renal fibrosis and macrophage infiltration. These data suggest that C21 may counteract tubulo-interstitial fibrosis, the most potent predictor of the progression of renal diseases

Clinical significance of epithelial-to-mesenchymal transition in laryngeal carcinoma: Its role in the different subsites

Background: During epithelial-to-mesenchymal transition, cancer cells lose adhesion capacity gaining migratory properties. The role of the process on prognosis has been evaluated in 50 cases of laryngeal carcinoma. Methods: E-cadherin, N-cadherin, β-catenin, α-catenin, γ-catenin, caveolin-1, and vimentin immunohistochemical expression were evaluated using a double score based on staining intensity and cellular localization. Results: Cytoplasmic E-cadherin and α/γ catenin staining were associated with a decrease in survival, cytoplasmic β-catenin was associated with advanced stage, and N-cadherin and vimentin expression were associated with poor differentiation and tumor relapse. On the basis of cancer cells, epithelial or mesenchymal morphological and immunophenotypic similarity we identified 4 main subgroups correlated with a transition to a more undifferentiated phenotype, which have a different pattern of relapse and survival. Conclusion: The negative prognostic role of epithelial-to-mesenchymal transition has been confirmed and a predictive role in glottic tumors has been suggested, leading us to propose epithelial-to-mesenchymal transition as an additional adverse feature in laryngeal carcinoma

Government guarantees and financial stability

Banks are intrinsically fragile because of their role as liquidity providers. This results in under-provision of liquidity. We analyze the effect of government guarantees on the interconnection between banks' liquidity creation and likelihood of runs in a global-game model, where banks' and depositors' behavior are endogenous and affected by the amount and form of guarantee. The main insight of our analysis is that guarantees are welfare improving because they induce banks to improve liquidity provision, although that sometimes increases the likelihood of runs or creates distortions in banks' behavior

Resonant, broadband and highly efficient optical frequency conversion in semiconductor nanowire gratings at visible and UV wavelengths

Using a hydrodynamic approach we examine bulk- and surface-induced second and third harmonic generation from semiconductor nanowire gratings having a resonant nonlinearity in the absorption region. We demonstrate resonant, broadband and highly efficient optical frequency conversion: contrary to conventional wisdom, we show that harmonic generation can take full advantage of resonant nonlinearities in a spectral range where nonlinear optical coefficients are boosted well beyond what is achievable in the transparent, long-wavelength, non-resonant regime. Using femtosecond pulses with approximately 500 MW/cm2 peak power density, we predict third harmonic conversion efficiencies of approximately 1% in a silicon nanowire array, at nearly any desired UV or visible wavelength, including the range of negative dielectric constant. We also predict surface second harmonic conversion efficiencies of order 0.01%, depending on the electronic effective mass, bistable behavior of the signals as a result of a reshaped resonance, and the onset fifth order nonlinear effects. These remarkable findings, arising from the combined effects of nonlinear resonance dispersion, field localization, and phase-locking, could significantly extend the operational spectral bandwidth of silicon photonics, and strongly suggest that neither linear absorption nor skin depth should be motivating factors to exclude either semiconductors or metals from the list of useful or practical nonlinear materials in any spectral range.Comment: 12 pages, 4 figure

Meet, Discuss and Trust each other: large versus small groups

In this paper we propose a dynamical interpretation of the sociological distinction between large and small groups of interacting individuals. In the former case individual behaviors are largely dominated by the group effect, while in the latter mutual relationships do matter. Numerical and analytical tools are combined to substantiate our claims.Comment: 12 pages, 4 figure

Sustainable water resources management to combat desertification in the Nurra region, northwestern Sardinia, Italy

Sustainable water management plays an important role in the frame of the multidisciplinary research activities aiming to combat or to mitigate the desertification processes. The study activities have been carried out by RIADE Research Project (Integrated Research for Applying new technologies and processes for combating Desertification, www.riade.net. RIADE was co-financed by MIUR within the National Operative Programme 2000-2006. The primary objective was to explore and to develop models and strategies for innovative and sustainable solutions of water resources management, adopting a multidisciplinary approach, at the catchment and hydrogeological basin scale in a Mediterranean context, using a case history of a pilot area in NW Sardinia (Italy). The high concentration of population in this coastal zone and the intense agricultural activity have determined a relevant increase of water demand. This demand is generally satisfied by surface water, but, in some peculiar dry periods, it exceeds the available quantities. In these critical periods, groundwater are the only alternative source constituting a strategic water resource. The groundwater chemical properties are then correlated with the effects of the anthropogenic pressures. The used approach shows the application of groundwater protection criteria, in accordance with EU policies, and it was aimed to develop a methodological tool which can be applied to different scenarios

Accurate and fast 3D interactive segmentation system applied to MR brain quantification

This work presents an efficient interactive segmentation system for volumetric data-sets based on advanced 3D morphological analyses and an interaction paradigm that allows a good match with user intentions. This system has been designed to produce accurate results under the complete control of the user, to minimize the interaction time and to address a generality of 3D segmentation tasks. The system has been tested and compared with other softwares on normal MR brain structure quantification and on a challenging clinical setting pointed to the detection of the presence of subtle brain atrophy associated to primitive immunodeficiency (PID)

New aspects in limestone dissolution for wet flue gas desulfurization

Fortsättningsvis tillgodoses största delen av världens energibehov genom förbränning av fossila bränslen, dessutom forsätter världens totala energibehov att öka. Eftersom förbränning av fossila bränslen som t.ex. olja och kol orsakar utsläpp av svaveldioxid som är skadligt för både människa och natur, finns det fortfarande ett akut behov av forskning och utveckling av metoder för svavelrening. De vanligaste teknikerna för svavelrening är våt- och semitorrskrubbning, där svaveldioxiden absorberas av en skrubbervätska. Det är allmänt känt att våtskrubbning är en av de effektivaste teknikerna för svavelrening både ekonomiskt och tekniskt sett samt den mest använda. Våtskrubbningsprocessen har dock flera nackdelar, som dess höga vatten- och energiförbrukning. I större kraftverk går ca 1-3% av dess eleffekt åt till rökgasreningsprocessen, vilket kraftigt motiverar utveckling av nya reningsprocesser samt effektivering av existerande reningsanläggningar. Skrubbervätskan som till huvudsak består av vatten innehåller vanligtvis även kalcium vars syfte är att binda svavlet. Kalciumet kan tillsättas i flera former varav bränd kalk och kalksten är de vanligaste formerna. Kalksten används ofta i svavelreningsprocessen p.g.a. dess låga pris och för att den ger upphov till den användbara biprodukten gips. Kalkstenens upplösningshastighet är en de av faktorer som kraftigast påverkar reningsprocessen. En detaljerad experimentell karakterisering och analys av kalkstenspartiklar i fast form och i vätskeform har utförts i detta arbete. En experimentell metod för att studera kalkstenens upplösningshastighet vid låg till obegränsad massöverföring har även utvecklats i detta arbete. Metoden möjliggör identifieringen av systemoberoende kinetiska parametrar, vilka kan användas för att undersöka reningsprocesser samt för att planera nya reningsanläggningar. Kinetiska modeller utvecklades genom att använda kalkstenpartiklars specifika yta, som mättes genom kväveadsorption. Efter att de kinetiska parametrarna bestämts experimentellt utvecklades en skrubbermodell för att optimera en i driftvarande skrubber. Genom att kombinera experimentellt bestämda modeller med matematisk optimering erhölls en djupare insikt i hur olika råmaterial påverkar processen och hur driftparameterar bör justeras för att minska elförbrukningen

Measuring the mixing efficiency in a simple model of stirring:some analytical results and a quantitative study via Frequency Map Analysis

We prove the existence of invariant curves for a $T$--periodic Hamiltonian system which models a fluid stirring in a cylindrical tank, when $T$ is small and the assigned stirring protocol is piecewise constant. Furthermore, using the Numerical Analysis of the Fundamental Frequency of Laskar, we investigate numerically the break down of invariant curves as $T$ increases and we give a quantitative estimate of the efficiency of the mixing.Comment: 10 figure